Multiple congressional sources tell CBS News that the two sides have agreed on an income threshold for the expiration of the Bush-era tax cuts for the wealthiest Americans: $400,000 for individuals and $450,000 for families. For weeks, Democrats have pushed for letting the cuts expire for those making over $200,000 and families making over $250,000 while Republicans have wanted to renew the cuts for all Americans, including the wealthiest.

Additionally, agreement has been reached on the estate tax, which was set to increase from 35 percent to 55 percent in 2013. Instead, the compromise sets the new rate at 40 percent with the first $5 million exempt from being taxed.

Vice President Joe Biden and Senate Majority Leader Mitch McConnell, R-Ky., have been the key negotiators over the past 24 hours and the movement on taxes represents a huge step forward in the talks.